Polyurethane foams with a more flame-resistant finish have long been sought and, because flame resistance requirements are becoming increasingly more stringent, continue to receive attention. As a result, particular attention has recently been paid to British Standard BS 5852, Part 2, for example in the performance of the Crib 5 test. This test imposes particularly stringent demands on the foams in regard to their ignition resistance. In addition to the more stringent flame resistance requirements, restricted use of phosphate esters or haloalkyl phosphate esters as flameproofing agents is being urged.
Another approach to flameproofing polyurethane foams uses melamine as a flameproofing agent. In this regard, see German Offenlegungsschrift 2,809,084, British Patent 2,177,406, German Offenlegungsschrift 2,815,554, German Offenlegungsschrift 3,530,519 and British Patent 2,094,315. However, melamine makes the foams relatively hard, as reflected by a considerable increase in the compression hardness of the foam.
German Offenlegungsschrift 2,533,180 relates to the production of flame-retardant latex or polyurethane foams using aluminum oxide hydrate, other bauxite minerals, and oxamide. Since, oxamide itself does not have a flameproofing effect in conventional polyurethane foams, the self-extinguishing effect cannot be attributed to oxamide.
On the other hand, if these compounds are used in high-resilience (HR) foams, a surprisingly good flameproofing effect is observed. Moreover, if amide-containing compounds having a chain length longer than for oxamide, excellent flameproofing is obtained in both standard foams and high-resilience foam systems.